Angiogenesis is a physiological process of growing new blood vessels from pre-existing vessels. It takes place in a healthy subject to heal wounds, i.e., restoring blood flow to tissues after injury or insult.
Excessive angiogenesis may be triggered by certain pathological conditions such as cancer, age-related macular degeneration, and chronic inflammatory disease. As a result, new blood vessels feed diseased tissues and destroy normal tissues. In cancer, new blood vessels also allow tumor cells to escape into the circulation and lodge in other organs.
Vascular endothelial growth factor (VEGF), a homodimeric glycoprotein, and its receptors, e.g., kinase insert domain receptor (KDR), constitute an important angiogenic pathway. Studies have shown that inhibition of KDR resulted in endothelial cell apoptosis and, thus, suppression of angiogenesis. See Rubin M. Tuder, Chest, 2000; 117: 281. KDR inhibitors are therefore potential candidates for treating an angiogenesis-related disorder.